1. Technical Field
The present invention is related to a viral vaccine against rabies and use of the virus for producing rabiesvirus immunobiologicals. More particularly, the present invention is related to a genetically engineered plasmid vector that has been used to construct a unique vaccinia poxvirus infectious recombinant for expressing in animals or in tissue cultures part or all of the gene for rabiesvirus glycoprotein. Such a recombinant employing vaccinia or other poxviruses, could be used for production of rabies vaccine, live or inactivated, as well as for production of rabiesvirus glycoprotein antigen, antibody or other related biochemical or immunological reagents.
2. State of the Art
Rabies vaccines presently in use generally contain preparations of inactivated or attenuated live rabiesvirus. Such preparations might be relatively costly, biologically unstable or produce vaccinal side effects. Recently, the cloned cDNA of the glycoprotein (G) gene of the ERA strain of rabiesvirus (Anilionis et al. 1981 Nature 294:275-278) was expressed by infecting mammalian cell cultures with a recombinant of the Copenhagen strain of vaccinia virus (Kieny et al. 1984 Nature 312:163-166; Wiktor et al. 1984 PNAS 81:7194-7198). To produce the recombinant, the G cDNA had been directed into the vaccinia thymidine kinase (TK) locus essentially by genetic recombination method (Mackett et al. 1982 PNAS 79:7415-7419; Mackett et al. 1984 J. Virol. 49:857-864) with a bacterial plasmid construct that contained cDNA of ERA G flanked by vaccinia TK sequences. Expression of G was regulated by having inserted proximal to G cDNA the commonly used vaccinia gene promoter for the 7.5 kilodalton (kD) protein (Mackett et al. 1984 ibid.). Mice and rabbits that were vaccinated with this recombinant virus (VVTGgRAB26D 3) produced neutralizing antibodies and were protected against rabiesvirus challenge. However, the Copenhagen strain of vaccinia, the vector for expression of the rabiesvirus strain ERA G cDNA, is most likely to be unsuitable for vaccine purposes because it has been associated with a relatively high frequency of encephalitic vaccinal complications in humans when used for immunoprophylaxis of smallpox (Polak 1973 Int. Symp. on Smallpox Vaccine, 1972 Bilthoven, 19:235-242, Karger, Basil; vonMagnus 1973 Int. Symp. on Smallpox Vaccine, 1972 Bilthoven 19:227-233, Karger, Basil) and has relatively more apparent pathogenicity for laboratory animals compared to other vaccinia strains (Andersen 1969 Proc. Symp. on Smallpox, pp. 53-64, Yugoslav Acad. Sci., 1969 Zagreb, Yugoslavia). Hence, the need remains to provide for humans and animals an efficacious vaccine against rabies that would be potent, less perishable, less costly and having diminished or no vaccinal side effects compared to the presently utilized rabies vaccines. A vaccinia--based vaccine, such as strains Lister and New York Board of Health which have been used with relatively low side effects during the eradication of smallpox, appears to possess such attributes. (Arita and Fenner, 1985, "Vaccinia Virus as Vectors for Vaccine Antigens," pp. 49-60, G. Quinnan ed., Elsevier, N.Y. Recombinants derived with these strains and used for vaccine could also be readily adapted for production of related antigen, antibody and other immunobiological reagents. However, whether recombinants made with the more attenuated vaccine strains could protectively immunize against rabiesvirus infection, cannot be a priori predicted. Increased expression of immunogen genes such as rabiesvirus G could be gained by incorporating poxvirus DNA control elements that would regulate higher levels of protein production than currently achieved by use of promotor P.sub.7.5.